Interactive displays most commonly use soft display means such as CRT's which provide an erasable image and which offer a facility for page composition manipulation so the image may be altered and evaluated prior to making the final printed copy. The image should substantially show the page text and graphics as it will appear in the final copy. The printed matter comprises the characters, the positions of the characters on the page, and any other printed matter which may be placed on the page layout.
In providing an interactive display, the character form size, and placement must be variable.
One of the difficulties and problems facing designers of interactive displays, was the need for a charactr data base which provide a normalized set of characters for enlargement and reduction and which could be rapidly accessed making the screen maximumly responsive to any changes. As the operator composes changes in the display, in an attempt to refine the display, the changes must be reflected rapidly on the screen to save composer time and reduce the composing cost.